Let us study the Q values associated with the removal of one or two nucleons from a nucleus. These are conventionally defined in terms of the one-nucleon and two-nucleon separation energies. The neutron separation energy is defined as $$ S_n= -Q_n= BE(N,Z)-BE(N-1,Z), $$ and the proton separation energy reads $$ S_p= -Q_p= BE(N,Z)-BE(N,Z-1). $$ The two-neutron separation energy is defined as $$ S_{2n}= -Q_{2n}= BE(N,Z)-BE(N-2,Z), $$ and the two-proton separation energy is given by $$ S_{2p}= -Q_{2p}= BE(N,Z)-BE(N,Z-2). $$